EXTRACV

This is part of the colvar module

Allow PLUMED to use collective variables computed in the MD engine.

This feature requires the MD engine to use special instructions to pass to PLUMED the value of some pre-computed collective variable. Check the documentation of the MD code to find out which collective variables can be computed and passed to PLUMED. These variables can then be accessed by name using the EXTRACV action.

Examples

This example takes the lambda variable pre-computed in GROMACS and apply to it a restraint to keep it close to the value 3.

Click on the labels of the actions for more information on what each action computes

l: EXTRACV 
NAME
compulsory keyword 
name of the CV as computed by the MD engine 
=lambda The EXTRACV action with label l calculates a single scalar value
RESTRAINT 
ARG
the input for this action is the scalar output from one or more other actions. 
=l 
KAPPA
compulsory keyword ( default=0.0 )
specifies that the restraint is harmonic and what the values of the force constants
on each of the variables are 
=10 
AT
compulsory keyword 
the position of the restraint 
=3 The RESTRAINT action with label 

Glossary of keywords and components

Compulsory keywords

NAME	name of the CV as computed by the MD engine